Question

Which is not the condition for the formation of echoes?

Options

• Minimum distance between the source of sound and reflecting body should be 17 m.

• The temperature of air should be above 20°C.

• The wavelength of sound should be less than the height of the reflecting body.

• The intensity of sound should be sufficient so that it could be heard after reflection.

Answer 1

The temperature of air should be above 20°C.

Explanation:

A particular air temperature is not a condition for hearing an echo. The reflecting body should be at least 17 m away, large enough compared with the wavelength, and the reflected sound must be audible.